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  1. #21
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    If the insert is a Shars one I would get a better quality one and try again, their inserts are crap IMO

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  3. #22
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    RueBear,
    If you install a turning bit/insert and travel/cut toward the tail do you get chatter?
    Does your insert seem fingernail shaving sharp?
    Does the top of cutting bit/insert have any clearance attitude like back rake , or side cutting edge rake?
    Your compound a little centered on you saddle, not far extended off to the left side?
    Tried another part holding device.
    Using some lubrication.
    Holding your bit/insert holder as short of hang-out/long as possible.
    Give everything a good shake/soft hammer tap with machine not running to see if everything is solid/tight?
    File check hardness of your part?
    In feeding with the compound dial, with compound at 30* or a tad less?
    Tool bit/insert traveling toward the chuck with this set-up and spindle top coming toward you?
    Seeing the chip mostly if not all flowing off the left edge of the bit/insert?
    know your chuck is tight fitted to the spindle.
    See jaw marking on the part to know the jaws are not wrong way tapered?
    Tried bringing in use of the tail stock center to see if that helps.
    Holding part not hanging way out?

    I know most of these if not all have been mentioned once or more.

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    Quote Originally Posted by RueBear View Post
    ...I have a slight vibration in the lathe which I believe is coming from the fairly light base the machine comes with.
    If you can rest your hand on the toolpost and feel the vibration, it's going to translate to the part.

    Try a lower RPM and see if the finish improves.

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  6. #24
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    michiganbuck-Tried bringing in use of the tail stock center to see if that help

    One of many great tips from mb, that one would help eliminated some spindle problems hard to detect otherwise. Even at 1700lbs, its a light machine that makes this mb tip important- Does your insert seem fingernail shaving sharp? I would suggest follow the rest of them also.

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    Add to the list: Shim seat solid and not the pocket washed out near front under the insert so screw is holding insert straight but insert not solid underneath. Put a small .002 shim under the leading edge of shim seat and screw down on that, with not over-tightening the screw so not to crack/break the insert. cutting action will hold it down tight if needed. be sure the insert is tight to the pocket back sides so not held away by the screw, shim there if needed.. insert pocket floor flat not a high belly (convex).

    Yes If you tried HSS bit the not likely the holder but still good to check.

    Can you add some solid legs going to the floor at the head stock end? / is the vibration a humm and a tap-tap kind of fee

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    I really appreciate all of the insight, yes I’ve looked at a lot these things, a few I haven’t. I’m gonna go ahead and try a better insert and a higher grade cutting oil. I’ll keep trying to diagnose the issue. I’m so close to having perfect threads. Got to get this last kink worked out. Thanks again everyone.

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    QT:[ I’m so close to having perfect threads.] What?

    If the part is file soft a (nail shaving) HSS bit should have worked.

    So maybe more than the insert.

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    Instead of trying a different insert why not try a hand ground HSS bit with some side rake. (No side rake if you are plunge cutting). You can try different side and back rakes to see if that will cure the chatter.

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    Quote Originally Posted by RueBear View Post
    I have ran lathes before in my younger years at a machine shop. I recently purchased a 1700lbs lathe and have had great success other than a few minor issues. One being that I can not for the life of me get all of the chatter out of my single point threading. I have the correct set up, my brother-in-law is a machinist...a good one, and he can’t figure it out either. So I’m guessing it is in my tooling at this point. Any advice is welcome, it is a stock lathe that bolted to the floor and leveled. Runout on both 3 and 4 jaw chucks are less than .0003. Stock tool post, Shars tool holders and tooling. I have adjusted spindle bearings, backlash and the gibs. I have a slight vibration in the lathe which I believe is coming from the fairly light base the machine comes with. Thought about bolting lathe to the wall with all thread for stability. Please advise.
    New to you lathe, but at 1700 pounds, ought to be able to thread.

    I had similar problems with a new old lathe ten years ago, and it turned out that the spindle preload was slack, allowing the spindle to squirm around. Also needed to ensure that everything from lathe bedways to single-point tool was tight.

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    Tape shim is a good idea but I'd go with a strip of soda can as a shim. Especially with jaws that leave marks on the work.

    Resonance is a bitch; ever try pushing a person on a swing not pushing at the end of the swing but someplace. End is much easier as that is resonance or in sync.

    If you have a collet setup for the lathe it might be worth a try.

    The idea of bypassing the comp'd for test purposes sound good. Rigid is always better.
    Look up the speeds and feeds for carbide inserts. Usually they are fast enough to make manual control difficult but then I'm an old guy.
    Coolant/lube on an open lathe is always a mess but can help finish and or tool life.
    Keep searching you'll find a sweet spot.

  14. #31
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    It appears that you've examined 99% of the potential problem causes.
    What I would look at is the tool post.
    Now I hate Shars with a passion,but once in a while you get lucky.Could it be possible that the tool post is "loose" or vibrating?
    Sometimes you can tighten up a tool post even with a cheater bar,but still have it be loose or not sitting flat like it should be.
    This will no doubt cause vibration and chatter with the smallest of cuts.

    Then I would check the gibs of the compound.

  15. #32
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    Does the lathe part off ok? What about somewhat heavy turning/facing? If it does both well that eliminates a lot of things and points to gear train and tool. If both of those are a struggle as well could be spindle bearings for sure.

  16. #33
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    I get great finishes on facing, turning, and I haven’t noticed any issues on parting. So, does that lead me back to my cheap tool post?

  17. #34
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    One more vote on getting some good inserts, like Carmex. I had some of the imports, had issues, went back to Carmex, threw out the import inserts.


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